An existing heat exchanger includes multiple tubes for a first fluid to flow and fins which promote heat exchange between the first fluid and a second fluid that flows around the tubes along one direction. Such a heat exchanger is disclosed, for example, in Patent Document 1. In the heat exchanger of Patent Document 1, each fin includes a plate-like planar portion along the one direction and multiple louvers which are parallel to one another and twisted up so as to incline with respect to the planar portion.
The second fluid flows a clearance between every pair of the adjacent louvers. A louver interval between some of the louvers is made wider than a louver interval between the other louvers. Hence, when viewed in the one direction, a louver height from the planar portion is not equal in all of the louvers. The louver height becomes higher as the louver interval becomes wider in one of a pair the louvers between which the louver interval is formed.
In the heat exchanger of Patent Document 1, the fin includes multiple louvers which are parallel to one another and twisted up so as to incline with respect to the one direction. The second fluid flows a clearance between every pair of the adjacent louvers and an interval between some of the louvers is made wider than an interval between the other louvers.